My day job is a
Safety Manager in a large manufacturing facility. One of the safety issues I
deal with at work is the prevention of hearing loss. The corporate Hearing
Protection Program includes annual employee audiometric testing as well as
location sound surveys and the implementation of hearing protection policy and
equipment to protect the employees from excess exposure to noise.

Part of my job is to
ensure the hearing protection equipment we use is sufficient to protect
employees against the high noise levels they are exposed to in different areas
of the plant.

It was during this
task I realized just how effective sound suppressors are at reducing the level
of sound reaching a shooter’s ear. In fact a reasonable sound suppressor is a
great deal more effective at preventing shooting related hearing loss than any
earplugs or muffs.

Consider that most
foam type earplugs have an NRR (Noise Reduction Rating) of 29-32 dB. Most PVC
type earplugs have NRR’s in the 25-27 dB range and earmuff performance varies
widely from 20-30 dB depending on the model.

Hearing protection is
rated by the NNR system developed by the EPA. Each device is tested and given
an appropriate number representing its noise reduction capability.

Industrial OH&S
standards for calculating noise reduction from a hearing protection device
require the NRR rating number to be reduced by 7 dB. The 7 dB subtraction is
made because the NRR is assigned under ideal conditions in a laboratory
setting. Therefore, it doesn’t necessary reflect the device’s actual noise
reduction in the real world.

The internationally
recognized limit for hearing damage from impulse sound is 140 dB. To ensure no
hearing damage can occur, a hearing protection device must reduce noise exposure
at the ear to 140 dB or less.

Lets have a quick
look at the real world performance of the three types of hearing protection:

Device

NRR

Less 7 dB

Max SPL

Foam
Plugs

29-32

22-25

162-165

PVC Plugs

25-27

18-20

158-160

Muffs

20-30

13-23

153-163

The Max SPL column
shows the maximum noise level the hearing protection device can protect from.
Above this level, noise greater than the 140 dB limit is still reaching the ear.

The real world
performance of typical hearing protection devices are not very impressive. All
rifle cartridges from the 223 Remington and up produce a muzzle signature louder
than 165 dB.

That means even the
best hearing protection devices are potentially exposing shooters to noise
levels high enough to cause permanent hearing damage. Add in a muzzle brake or
the confines of a shooting range and the noise level at the shooter’s ear
increases even more as sound waves are reflected back towards the shooter.

On the other hand,
the majority of modern sound suppressors are capable of reducing the muzzle
signature of all but the biggest cartridges down to the 140 dB limit. Typically
only the .338 Lapua and .50 BMG are intense enough to require hearing protection
on a suppressed rifle.

Suppressor sound
measurements are taken one meter to the left of the muzzle. Sound levels at the
shooter’s ear are typically a few decibels lower than the official muzzle
signature rating because suppressors direct residual noise forward.

Some suppressor
manufacturers are even advertising their products meet government standards for
noise reduction. None of the hearing protection devices I am aware of can make
this claim with respect to high intensity impulse noise. I have been shooting
for more than 15 years and have never heard any sort of claim regarding the
hidden danger of hearing protection devices. It was only when my job and my
interest coincided that I became aware of this information.

Sound suppressors
also protect the hearing of bystanders and prevent the painful experience of
being exposed, unprotected to an unexpected shot. Sound suppressors in the
hunting field reduces the public’s exposure to annoying gunshots and totally
prevent the hunter’s exposure to the shot when there is not time to put on
hearing protection.

Countries and
governments that do not allow their citizens access to sound suppressors are
causing the citizens under their protection to be exposed to harmful sound
levels during recreational hunting and shooting activities. British hunters and
shooters sued their government on Occupational Health & Safety grounds for the
right to use sound suppressors as hearing safety equipment and they won.

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